Eureka my dear I have just figured out your problem (mainly because I just played up to this part again)
You didn't open the grate into the conveyor room from the maze did you? If you click on it does Chewy tell you it can only be opened from the inside? If so, that's the problem - it's still bolted shut.
Here's what you need to do - go back down into the Bork's HQ - back out the door you came in (where you put the Shuremy down) - back to the rope - climb the rope and go back into the maze - then go down the third corridor from the top - all the way to the end you will find a grate - open it and if you walk through it (not necessary but if you want to check) you will find yourself on the conveyor belt. Now just go back through the maze to where you went through the grate that has the rope - climb down - through the door by the tubes - through the other door in the HQ and out the walkway etc. etc. until you get to the conveyor belt room - go through that grate - and head out of the maze through the first walkway and to the left. You are now at the glider with the force shield down - whew